Users search online for various kinds of information, including recommendations to products and services. For recommendations, users tend to give more weight to recommendations from people they know, e.g., the more the users know the recommenders the higher the weight.
On the other hand, some people who provide recommendations may not want to reveal their identities. For example, these people may want to recommend doctors, dentists, lawyers, etc. to their friends and acquaintances but may not want their friends and acquaintances to know that they use these service providers, which include, for example, a doctor specializing in a certain field.